Not enough energy
The first aircraft carrier catapults were actually powered by compressed air, not steam, and presumably something similar is still possible.
A typical aircraft of the 1910-20 period suitable for launch from an aircraft carrier would weigh a couple of tonnes with a low takeoff speed. A mission-ready F-35B or indeed any existing strike fighter can weigh up to 25 tonnes loaded for a mission and can require the plane to be travelling at over 150mph at the end of the catapult to clear the front of the carrier successfully and avoid becoming a sea dart (tm).
Finding space to fit air or steam plant into the existing carrier spaces and the surplus power to produce stored energy to launch aircraft using some kind of catapult wasn't really a goer for the QE-class carriers. The EMALS electromagnetic launcher was a possibility, it has a lot of good features but it also sucks a lot of electrical power and the QE-class gas turbine engines weren't specced to produce bursts of surplus energy of that size. Some kind of battery/spinning storage might work but again there wasn't much space left to put it somewhere in the hull and if it ever broke then nothing could be launched at all.
Biting the hand that feeds IT
